Modification of a phospholipid stabilized emulsion interface by bile salt: effect on pancreatic lipase activity

Abstract

Lipase is activated by binding to an insoluble emulsified or aggregated substrate. The extent of binding is related to the physicochemical as well as the compositional structure of the interface, the quality of the interface. 'Quality' is as yet undefined but thought to contain contributions from electrostatic interactions, orientation of substrate, and hydration forces. To investigate the electrostatic and compositional factors we have used olive oil-in-water emulsions prepared with phosphatidylcholine and four bile salts of varying hydrophobicities. By measurement of the droplet zeta potential we have monitored semi-quantitatively the incorporation of bile salts within the interface. No correlation was found between droplet surface charge as monitored by the zeta potential and lag phase. The duration of the observed lag phase was found to be inversely related to the degree of incorporation of the bile salts. Simultaneously there was evidence of lipase binding to monomeric bile salts, reducing its availability for adsorption. Calcium ions reduced the surface charge but there was no correlation with lag phase duration. The evidence presented here agrees with a more specific role for calcium ions, i.e., the formation of a new catalytically active enzyme complex, (enzyme)-(mixed micelle)-(calcium ion).

Preparation and characterization of nanoemulsions of curcumin and echium oil

“…Zero order kinetics are applied for lipolysis process. Therefore, enzyme binding increases with the increased product concentration due to the alteration of emulsion interface (Wickham et al, 1998). Incremental FFA release could be explained by increased lipase dispersion between the aqueous phase and the emulsion interface as lipase was activated when binding to an insoluble emulsified substrate.…”

Interfacial structure and stability of food emulsions as affected by protein–polysaccharide interactions

“…The situation is greatly complicated, of course, by the various additional interactions with saliva, gastric juices, etc., and by various kinds of interfacial complexation and competition at the oil-water interface involving small-molecule surfactants, either present in the original food or released during digestion (phospholipids, bile salts, etc.). 123,124 Despite this complexity, it is reasonable to anticipate that the key principles already established in model biopolymer studies in vitro will have applicability under the physiological conditions existing when real food colloids are eaten and digested.…”

Transitions in the internal structure of lipid droplets during fat digestion

“…7 Bile salts (BS) help to stabilize the emulsion droplets and modify the oil/ water interface for the adsorption of the lipase-colipase complex. 13 It has been reported that the lipolysis rate of triglycerides increases with BS concentration. 14 BS concentration in the gall bladder is between 10 and 50 mmol l À1 , in the intestine around 4-20 mmol l À1 , depending on the state (fasted or fed).…”